Sunday, January 31, 2010

Jupiter's Layers of Gas

On July 13, 1995, Galileo released an atmospheric probe, which plunged into Jupiter’s atmosphere and transmitted data for almost an hour before it was destroyed by intense atmospheric heat and pressure. After analysis of this data (and earlier data from Voyager), astronomers concluded that Jupiter’s atmosphere is arranged in distinct layers. Since there is no solid surface to call sea level, the troposphere (the region containing the clouds we see) is considered zero altitude, and the atmosphere is mapped in positive and negative distances from this. Just above the troposphere is a haze layer, and just below it are white clouds of ammonia ice. Temperatures in this region are 125–150 K. Starting at about –40 miles (60 km) below the ammonia ice level is a cloud layer of ammonium hydrosulfide ice, in which temperatures climb to 200 K. Below this level are clouds of water ice and water vapor, down to about –60 miles (100 km). Further down are the substances that make up the interior of the planet: hydrogen, helium, methane, ammonia, and water, with temperatures steadily rising the deeper we go.